Our rented apartment has double pane windows in PVC frames. They are of good quality, I think. However, during the current weather (lots of rain and heavy winds), two windows let in some water. It seems to be coming from the bottom of the frame. How do I figure out where the water is actually going through?

On the outside there are these little inlets -- I guess for allowing air exchange and letting humidity out? I have actually no idea. The inlets are tiny: about 2cm x 1cm and have a little rain cover.

Could the water be getting in through this? Can a carpenter/window maker repair this?

2 Answers 2


I would suggest the opposite of wallyk. Instead of trying to back track the leak, which probably goes through sealed off areas, try to reproduce it. Dry it, then use a hose on different parts of the outside window, once you have identified what part of the window is admitting the water, look for any ingresses. You basically need to divide the possible areas the water could be coming entering into zones, and then test each zone separately. Once you KNOW which exterior zone is responsible, then you can look for cracks.

  • I agree, this can be a good method. If you are lucky, the delay between spraying water somewhere and seeing it at the unwanted place is not more than a few minutes.
    – wallyk
    Jan 10, 2015 at 0:39

Tracing water leaks is one of the most challenging things that one might have to do with a structure.

Water can travel quite a distance and in completely non-intuitive paths. It is especially difficult to trace where two materials are butted against each other, like a pair of 2x4s side by side. In this situation, water can travel laterally or upward through capillary action (also known as wicking), as well as down.

How to do it varies considerably depending on circumstances. However, you might try a bright light shone where you see water and try closely watching for movement. Sometimes wiping a small part of it is needed to introduce a break so you can see its movement. Follow it upstream as far as you can. When (not if) you lose the trail, make a best guess where it is coming from and try to reacquire it there. Repeat.

Being successful may require a lot of patience. In one place I know of, the management company spent over $20,000 for experts to trace a slow drip into the middle of a condominium ceiling on the first floor. It turned out to be a window on the second floor about 25 feet away. The investigation involved tearing up a lot of decking, ceiling, two doorways, and a lot of closets.


Tyler's suggestion is a good one, but not very convenient nor comfortable during stormy weather. But you might try the inverse: Obtain a tarp (saran wrap, painting drop cloth, etc.) and cover the window exterior and see if that stops the water. If it does, maybe you can cover progressively less than the whole window to isolate the source.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.